The present invention relates to a flasher type fish sonar in which a circular board having a luminous body is rotated in a window of a display board.
In a prior flasher type fish sonar, a circular window is formed in the periphery of a display board provided with the front of a case, a luminous body mounted on a rotary disk is arranged opposite to the window, and the rotary disk is rotated by a motor. Brushes 8 are attached to slip rings provided with the rotary shaft of the rotary disk, an input circuit is connected to the brushes and a flasher display is constituted by these elements. A transmitting-receiving circuit is connected to the input circuit. When a signal from the transmitting-receiving circuit is input from the input circuit to the luminous body through the brushes and the slip rings, a part A becomes a starting point showing the surface of the sea, fishes are shown by parts B and C and the bottom of the sea is shown by a part D.
In the transmitting-receiving circuit, when output signals are input from a control circuit to a transmitting circuit, oscillating signals are input from the transmitting circuit to an ultrasonic transducer, and ultrasonic signals are emitted to the sea. When reflected signals from the sea are received by the ultrasonic transducer, the reflected signals are amplified by a receiving circuit, the amplified reflected signals are converted to digital signals in an analogue to digital converter, and the digital signals are input from the control circuit to a base of a transistor through a resistor of the input circuit of the flasher display. The base of the transistor is connected to the ground through a resistor. An emitter of the transistor is connected to the ground, a collector of the transistor is connected to the anode of the luminous body through a resistor, one of the brushes and the slip rings, and the cathode of the luminous body is connected to a direct current electric power source through the slip rings and the other of the brushes.
In the flasher type fish sonar, because the direct current electric power connected to the luminous body in the flasher display is constituted by a constant voltage circuit, when the digital signals from the control circuit are input to the base of the transistor of the input circuit of the flasher display, the electric current from the direct current electric power source flows to the luminous body through the other of the brushes and the slip rings and flows from the luminous body to the ground connected to the emitter from the collector of the transistor through the slip rings and the one of the brushes. Thus the electric current flowing to the luminous body is changed and the luminosity of the luminous body is changed when the contact resistance between the slip rings and the brushes is changed. When the change in the luminosity of the luminous body becomes high, a detection of fish is incorrectly viewed as the bottom of the sea.
It is, therefore, the primary object of the present invention to provide a flasher type fish sonar in which a constant current is input to a luminous body for eliminating a change of contact resistance between slip rings and brushes.
It is another object of the present invention to provide a flasher type fish sonar in which a constant current is connected to a luminous body for inputting constant current always.
In order to accomplish the above and other objects, the present invention comprises an ultrasonic vibrator for transmitting ultrasonic waves in the water and for receiving reflected signals in the water, a transmitting circuit for supplying oscillating signals to the ultrasonic vibrator, a receiving circuit for amplifying reflected signals received by the ultrasonic vibrator, an analogue to digital converter for converting the reflected signals to digital signals, an input circuit for inputting the digital signals from the analogue to digital converter by the control circuit, a flasher display consisting of a rotary disk having a luminous body mounted on a rotary disk rotating by a motor and a display board having a window displaying luminosity of the luminous body by inputting the digital signals from the input circuit through brushes connected to the input circuit and slip rings mounted on a rotary shaft of the rotary disk, the slip rings contacting the brushes, and a constant current circuit constituted in the input circuit, whereby changes of electric current flowing to the luminous body due to the contact resistance between the slip rings and the brushes is eliminated by the constant electric current from the constant current circuit.